Omudhome Ogbru, PharmD
Omudhome Ogbru, PharmD
Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.
Medical and Pharmacy Editor:
GENERIC NAME: tadalafil
BRAND NAME: Cialis
DRUG CLASS AND MECHANISM: Tadalafil is an oral drug that is used for treating impotence (the inability to attain or maintain a penile erection) and benign prostatic hyperplasia (BPH). It is in a class of drugs called phosphodiesterase-5 (PDE5) inhibitors that also includes sildenafil (Viagra) and vardenafil (Levitra). Erection of the penis is caused by the filling of the penis with blood. Filling occurs because the blood vessels that bring blood to the penis increase in size and deliver more blood to the penis, and, at the same time, the blood vessels that take blood away from the penis decrease in size and remove less blood from the penis. Sexual stimulation that leads to an erection causes the production and release of nitric oxide in the penis. The nitric oxide causes an enzyme, guanylate cyclase, to produce cyclic guanosine monophosphate (cGMP). It is cGMP that is primarily responsible for increasing and decreasing the size of blood vessels carrying blood to and from the penis, respectively, and causing an erection. When the cGMP is destroyed by another enzyme, phosphodiesterase-5, the blood vessels return to their normal size, blood leaves the penis, and the erection ends. Tadalafil prevents phosphodiesterase-5 from destroying cGMP so that cGMP stays around longer. The persistence of cGMP leads to a more prolonged engorgement of the penis with blood.
The mechanism whereby tadalafil improves the symptoms of BPH is not clear, but phosphodiesterase-5 also is present in the muscles of the bladder and the prostate, and it has been suggested that the relaxation of these muscles may make the passage of urine less difficult, for example, by reducing the pressure in the muscle surrounding the opening to the urethra that controls the flow of urine from the bladder. Tadalafil was approved by the FDA in November 2003.
GENERIC AVAILABLE: No
PREPARATIONS: Tablets: 2.5, 5, 10 and 20 mg.
STORAGE: Tadalafil should be stored at room temperature between 15 C to 30 C (59 F to 86 F).
DOSING: For most individuals, the recommended starting dose of tadalafil is 10 mg per day taken before sexual activity (tadalafil for use as needed). Depending on the adequacy of the response or side effects, the dose may be increased to 20 mg or decreased to 5 mg a day. The effect of tadalafil may last up to 36 hours. Individuals who are taking medications that increase the blood levels of tadalafil should not exceed a total dose of 10 mg in 72 hours (See drug interactions). For once daily use without regard to sexual activity the recommended dose is 2.5 to 5 mg daily. Tadalafil should not be taken more than once daily.
The recommended dose for BPH, or BPH and ED is 5 mg daily taken about the same time each day. Tadalafil may be taken with or without food since food does not affect its absorption from the intestine.
The dose of tadalafil may require adjustment for patients with reduced kidney or liver function.
DRUG INTERACTIONS: The breakdown and elimination of tadalafil from the body may be decreased by erythromycin, ketoconazole (Nizoral), itraconazole (Sporanox), indinavir (Crixivan) and ritonavir (Norvir). Therefore, these drugs may increase the levels of tadalafil in the blood. If these drugs are being used at the same time as tadalafil, the dose of tadalafil should be reduced to 10 mg every 72 hours when used as needed or 2.5 mg when used daily in order to avoid side effects from high levels of tadalafil.
Rifampin, carbamazepine (Tegretol, Tegretol XR, Equerto, Carbatrol), phenytoin (Dilantin, Dilantin-125), and phenobarbital may decrease blood levels of tadalafil, possibly reducing the effect of tadalafil.
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